More than half of the world's populations have no physical address. This is something we, in the developed parts of the world, take for granted and spend very little time thinking about.
But, if you think about it, why is it so imprtant? If there is a medical emergency, where do you tell the ambulance to go? If you buy a cellphone, do you have to give proof of address? If you open a bank account, do you have to provide proof of address? If you order something online, where do they deliver the parcel? If you register a business, what address to you put on the form? If you have a business, where are your orders delivered to? How do you send out invoices with no address?
The above is just some of the examples that these people can not do, because they have no way of indicating or providing proof that they reside at a certain location.